/*
 * Copyright 2007-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.paoding.rose.web.instruction;

import java.io.IOException;

import javax.servlet.ServletException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import net.paoding.rose.impl.util.PlaceHolderUtils;
import net.paoding.rose.web.Invocation;

/**
 * 
 * @author qieqie.wang@paoding.net
 * 
 */
public abstract class AbstractInstruction implements Instruction {
	protected Log logger = LogFactory.getLog(getClass());

	protected Instruction preInstruction;

	protected String resolvePlaceHolder(String text, Invocation invocation) {
		return PlaceHolderUtils.resolve(text, invocation);
	}

	@Override
	public final void render(Invocation invocation) throws IOException,
			ServletException, Exception {
		preRender(invocation);
		if (preInstruction != null) {
			preInstruction.render(invocation);
		}
		doRender(invocation);
	}

	protected void preRender(Invocation invocation) throws IOException,
			ServletException, Exception {
	}

	protected abstract void doRender(Invocation invocation) throws IOException,
			ServletException, Exception;

}
